Monday, February 23, 2015

Power Shortage - Alternatives and Solutions

The Problem: Our Four Wheel Camper’s power demand is often greater than our battery (2x group-24 AGMs) can supply.

Discussion: The fridge (4 to 5 amps while running) and the furnace (4 amps) are our two largest power users. Lighting is inconsequential as everything is LEDs with little demand. Between the two biggies, we can use somewhere about 50, 60, or more amp/hrs in a 24 hr. period during winter months. Since we have 75 amp/hrs available (50% of total battery capacity of 150 amp/hrs), you can see that just one day can chew up a good percentage of what we have. The solar panel (100 watts) is mounted flat on the roof so the angle to the sun is severe, especially in the winter. For maximum production, you’d want the panel pointing directly, squarely, at the sun. As it is, the panel will produce between 4 and 5 amps per hour on a sunny winter day here in Arizona… but that’s just for a few hours near midday. On a good day the system will pump a total of about 20 or 25 amp/hrs into the battery… about half of what we used. Now, depending on how much we drive, the truck’s alternator also charges the battery some. Short drives won’t add much, longer drives could get the battery back to 80% or so. In any case, we’re going downhill each additional day out.

Was it a mistake to order the camper with a 12v/120v compressor fridge? Possibly, but I’m not convinced. Like so many things in RVing, it’s all about compromise... pros and cons. On the pro-side, a compressor fridge is arguably safer as there’s no propane burner and open flame. It’s also not necessary for it to be level -- it’ll operate fine at as much as 30 degrees out of level. Our experience over our first 70 nights out is that we get as level as we can in the site and leave it at that. We’ve never had to take extraordinary measures, use blocks or other hunks of flotsam or jetsam to prop up a corner of the truck/camper for the sake of the fridge. On the con-side, it uses a little more power than I anticipated.

The furnace is a furnace, and we really don’t use it all that much. It’s usually off during the night and is used mostly to warm things up in the morning. My guess is that it is only a small part of our energy shortfall. I’ve toyed with the idea of replacing it with a Wave-type catalytic, and may do that someday. But for now we’re going to leave the furnace as-is.

During our first few days (nights?) with the camper last summer we noticed this shortage of power when camped in a very wooded campsite for a few days. Of course there the solar panel was contributing very little if anything to the cause due to lack of direct sun. We like camping in wooded areas and are not about take that out of our repertoire

And then we have cloudy days, right? Could even be a few in a row. Can’t make solar power on cloudy days… at least not much.

Possible Solutions: 1.) more solar panels 2.) buy a generator 3.) plug into the grid more often

Discussion: More solar panels may help on ideal sunny days, but what happens on cloudy days, or when we’re camped under a forest canopy? More solar is out.

The generator idea means we’d have to find a place to store it on-board. Then there’s the necessary gasoline… where do we put that? And furthermore, I’ve been one of the first to look down my nose at people with generators. You know… those "generator people" out there… loud obnoxious machines belching smoke and fumes and noise… I can’t stand it. And they’re probably just watching television when they ought to be outside communing with nature. Those, those… generator people!!

Plugging into the grid more often… in our case, it’d be every 2nd or 3rd night. The on-board charger would top off the battery just dandy and we’d be good to go for another couple nights. Hmmm. This might be the solution… except that… we didn’t buy this rig with the intention of going to full-hookup RV parks or KOAs or fancy plug-in campgrounds. We bought it so we could be off the grid, offline, for days and days in a row… lost up some lonely dirt road near the top of a mountain… a small clearing next to a babbling brook or splashing stream... places people rarely go. That’s why we bought it. So, NO, we’re not going to plug-in more… or at all if we can help it.

Our Solution: We put all this information into a couple big computing machines and let it grind away for a few days. We talked. We debated. We played “what-if” games, not to mention a few hands of "gen"rummy. And we decided to buy a generator.

Not just any generator, but a little Honda 1000. Why? First, we found that a Honda 1000 will fit perfectly into one of the bins under a dinette seat. Fit’s like a fine leather glove... like the bin was designed with that in mind. Second, was the fact that this little genny makes almost no noise (you almost have to feel it make sure it’s running), uses almost no gas (the half gallon tank lasts 6 or 8 hours), what little exhaust it makes smells like root beer extract (must be a Honda thing… would I kid you?), and it’s as light as a feather (under 30 lbs… OK, a large feather). It will power anything we have on board -- easily handling the charger and fridge at the same time with hundreds of watts left over.

This is how we’ve used it the first two times during our Mojave NP trip: Every 2nd or 3rd morning, when the battery is down to near 50% (12.2 volts resting), we fire up the genny and plug it into the 120v input on the camper. The on-board 3-stage charger begins to “bulk” charge the battery… throwing in a heavy dose of amps and volts (I don’t know… 5?, 6?, 7?, solar panels worth of juice?). After just an hour the battery is at 60% to 80% of full charge and we shut the genny off, stow it, and let the sun (and the truck, if we’re driving that day) finish charging the battery during the day. It all works as I’d hoped… even better than I’d hoped.

How about carrying that extra gas? Won’t have to very often, if at all. As I said above, the genny’s gas tank holds a little over a half gallon, which I estimate will last about 6 hours at it’s easy running pace. That alone should last us a couple weeks at the hour every couple days rate. I did pick up a 30oz. MSR aluminum fuel bottle, the kind backpackers use for stove fuel, and found it fits snugly and securely in the vented propane compartment. But really, we stop for fuel every day or two anyway, and it’s an easy thing to top of the generator tank at that time. Keep it simple.

So bring on the cloudy days and the heavily wooded forest campsites. We’re ready for ‘em. And we won’t have to plug in to the grid, ever.